Information recording medium, recording/reproducing apparatus, and stamper

ABSTRACT

On an information recording medium, a data track pattern and a servo pattern composed of a concave/convex pattern including a plurality of convex parts are formed on at least one surface of a substrate and respective concave parts in the concave/convex pattern are filled with non-magnetic material. In the concave/convex pattern that constructs the data track pattern, the respective convex parts are formed concentrically or in a spiral. In the concave/convex pattern that constructs the servo pattern, a unit convex part length along a direction of rotation of the substrate is set so that a value produced by dividing the unit convex part length by a distance from a center of the data track pattern decreases from an inner periphery to an outer periphery.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information recording medium where adata track pattern and a servo pattern are formed by a concave/convexpattern and respective concave parts in the concave/convex pattern arefilled with non-magnetic material, a recording/reproducing apparatusequipped with such information recording medium, and a stamper formanufacturing such information recording medium.

2. Description of the Related Art

As one example of a recording/reproducing apparatus equipped with thiskind of information recording medium, a magnetic recording apparatus 20equipped with a discrete track-type magnetic disk is disclosed byJapanese Laid-Open Patent Publication No. H09-97419. The magnetic diskis produced by forming concentric recording tracks (“belt-like convexparts”) composed of a recording magnetic material (“magnetic material”)on one surface of a glass disk substrate (“substrate”). Guard band partsare also formed by filling spaces (concave parts) between the respectiverecording tracks with a guard band material (a non-magnetic material) tomake the magnetic disk smoother and to magnetically separate adjacentrecording tracks. When manufacturing such magnetic disks, first amagnetic material is sputtered onto one surface of the substrate to formthe recording magnetic layer. Next, after a positive-type resist hasbeen spin-coated so as to cover the recording magnetic layer andprebaked, the same pattern as the guard band parts is drawn using amatrix cutting apparatus and then developed. By doing so, a resistpattern is formed on the recording magnetic layer. After this, therecording magnetic layer is etched using the resist pattern as a maskand mask residual is then removed by an ashing apparatus. By doing so,recording tracks and a servo pattern (convex parts) composed of magneticmaterial are formed on the substrate. After this, a non-magneticmaterial is sputtered onto the substrate in this state. When doing so, asufficient amount of non-magnetic material is sputtered until therespective concave parts between the recording tracks are completelyfilled with the non-magnetic material and the respective recordingtracks are covered with the non-magnetic material. Next, the surface ofthe sputtered non-magnetic material is dry-etched to expose the uppersurfaces of the recording tracks from the non-magnetic material. Bydoing so, recording tracks and guard band parts become adjacent in analternating manner, thereby completing the magnetic disk.

SUMMARY OF THE INVENTION

By investigating the conventional magnetic disk described above, thepresent inventors discovered the following problem. With theconventional magnetic disk, after the non-magnetic material is sputteredso as to cover the recording magnetic layer (the recording tracks), thenon-magnetic material is dry-etched until the upper surfaces of theconvex parts such as the recording tracks and the servo pattern areexposed, thereby smoothing the surface. However, when a magnetic disk ismanufactured according to this method of manufacturing, there are caseswhere a large amount of non-magnetic material remains on the convexparts formed of the magnetic material (hereinafter, non-magneticmaterial remaining on the convex parts is also referred to as “residual”) in an outer periphery of the magnetic disk, resulting in the convexparts being thickly covered with the non-magnetic material.

As a specific example, as shown in FIG. 18, a magnetic disk 10 xmanufactured according to a method of manufacturing described above ismanufactured so that track pattern regions At, in each of which aconcave/convex pattern 20 t composed of a plurality of concentricrecording tracks is formed, and servo pattern regions Asx, in which aconcave/convex pattern 20 sx for tracking servo purposes is formed,alternate in the direction of rotation (the direction of the arrow R inFIG. 18) of the magnetic disk 10 x. In a recording/reproducing apparatusin which this type of magnetic disk is provided, the magnetic disk isnormally rotated at a fixed angular velocity during recording andreproducing. Accordingly, on the magnetic disk 10 x, the length of theservo pattern region Asx along the direction of rotation of the magneticdisk 10 x is set so as to become longer from the inner periphery of themagnetic disk 10 x to the outer periphery (i.e., the servo patternregion Asx widens toward the outer periphery of the magnetic disk 10 x)in proportion to the length on the magnetic disk 10 x that passes belowa magnetic head (not shown) per unit time. More specifically, as shownin FIGS. 19 and 21, the length of an outer periphery servo patternregion Asxo in an outer periphery region Axo is greater than the lengthof an inner periphery servo pattern region Asxi in an inner peripheryregion Axi in proportion to a distance from a center O (see FIG. 18) ofthe concave/convex pattern 20 t. As a result, on the conventionalmagnetic disk 10 x, a value produced by dividing the unit convex partlength by the distance from the center O is equal across the entirerange from the inner periphery to the outer periphery. Also, on thistype of magnetic disk, at positions an equal distance from the center O,the unit length of convex parts (a reference length for which one convexpart is detected when reading a magnetic signal: L1 xi, L1 xo in FIGS.20 and 22) in the direction of rotation for convex parts 21 sxi, 21 sxo(hereinafter simply referred to as “convex parts 21 sx” when nodistinction is required) of the servo pattern region Asx (theconcave/convex pattern 20 sx) is set equal to the unit length of concaveparts (a reference length for which one concave part is detected whenreading the magnetic signal: L2 xi, L2 xo in FIGS. 20 and 22) along thedirection of rotation for concave parts 22 sxi, 22 sxo (hereinaftersimply referred to as “concave parts 22 sx” when no distinction isrequired). As a result, on the magnetic disk 10 x, the ratio of the unitconvex part length to the unit concave part length is 1 across theentire range from the inner periphery to the outer periphery.

Accordingly, as shown in FIGS. 20 and 22, on this magnetic disk 10 x,the length L1 xo of the convex parts 21 sxo in the outer periphery servopattern region Asxo is longer than the length L1 xi of the convex parts21 sxi in the inner periphery servo pattern region Asxi in proportion tothe distance from the center O of the concave/convex pattern 20 t. Theapplicant has discovered a phenomenon whereby during the dry-etching ofthe non-magnetic material 15 to expose the respective convex parts 21sx, the greater the length of the convex parts 21 sx present below thenon-magnetic material 15 (i.e., the greater the width of theupper-surfaces of the convex parts 21 sx), the slower the etching of thenon-magnetic material 15 proceeds. For this reason, as shown in FIG. 20,when etching is carried out for the entire region of the magnetic disk10 x from the inner periphery to the outer periphery with etchingconditions set so that in the inner periphery servo pattern region Asxiwhere the length L1 xi is comparatively short, the residual (thenon-magnetic material 15) on the convex parts 21 sxi is removed and theinner periphery of the magnetic disk 10 x has favorable smoothness (thevalue of the surface roughness Ra is low, or the height difference Hxibetween the convexes and the concaves is small), as shown in FIG. 22,comparatively thick residual (the non-magnetic material 15) is left onthe convex parts 21 sxo in the outer periphery servo pattern region Asxowhose length L1 xo is comparatively long. Accordingly, when thenon-magnetic material 15 is etched with such etching conditions, thesurface roughness Ra (or the height difference Hxo between the convexesand concaves) in the outer periphery of the magnetic disk 10 x becomesextremely large.

Also, the present applicant has discovered a phenomenon where when thenon-magnetic material 15 is dry etched to expose the respective convexparts 21 sx, the greater the length of the concave parts 22 sx (i.e.,the greater the width of the concave parts 22 sx), the slower theetching of the non-magnetic material 15 on the convex parts 21 sx formedso as to sandwich the concave parts 22 sx proceeds. For this reason, asshown in FIG. 20, when etching is carried out across the entire rangefrom the inner periphery to the outer periphery with etching conditionsso that the residual (the non-magnetic material 15) on the convex parts21 sxi in the inner periphery servo pattern region Asxi where the lengthL2 xi of the respective concave parts 22 sx is comparatively short isremoved to achieve favorable smoothness for the inner periphery of themagnetic disk 10 x, as shown in FIG. 22, comparatively thick residual(the non-magnetic material 15) is left on the convex parts 21 sx in theouter periphery servo pattern region Asxo where the length L2 xo of therespective concave parts 22 sx is comparatively long. Accordingly, whenthe non-magnetic material 15 is etched with such etching conditions, thesurface roughness Ra (or the height difference Hxo of the convexes andconcaves) in the outer periphery of the magnetic disk 10 x becomesextremely high. In this way, for the conventional magnetic disk 10 x,there has been the problem that due to the convex parts 21 sxo beingthickly covered with the non-magnetic material 15 in the outerperiphery, the smoothness of the magnetic disk 10 x deterioratesremarkably in the outer periphery (i.e., as the distance from the centerO increases).

Also, for the conventional magnetic disk, during the manufacturingprocess, a resist pattern is formed by using a matrix cutting apparatusto draw an exposure pattern in a positive-type resist formed so as tocover the recording magnetic layer and then developing the resist. Whendoing so, since time is required to draw the exposure pattern, it isdifficult to quickly form the resist pattern (mask) for etching therecording magnetic layer. A faster method of producing the resistpattern is therefore desired.

The present invention was conceived to solve the problem described aboveand it is a principal object of the present invention to provide aninformation recording medium with favorable smoothness across an entirerange from an inner periphery to an outer periphery thereof, arecording/reproducing apparatus equipped with an information recordingmedium with favorable smoothness, and a stamper that can easily form aconcave/convex pattern for use during etching in a short time.

On an information recording medium according to the present invention, adata track pattern and a servo pattern composed of a concave/convexpattern including a plurality of convex parts are formed on at least onesurface of a substrate and respective concave parts in theconcave/convex pattern are filled with non-magnetic material, wherein inthe concave/convex pattern that constructs the data track pattern, therespective convex parts are formed concentrically or in a spiral, and inthe concave/convex pattern that constructs the servo pattern, a unitconvex part length is set so that a value produced by dividing a unitconvex part length along a direction of rotation of the substrate by adistance from a center of the data track pattern decreases from an innerperiphery to an outer periphery.

It should be noted that the expression “the respective convex parts inthe concave/convex pattern that constructs the data track pattern may beformed concentrically or in a spiral” in the present specificationincludes a data track pattern of a patterned medium where convex partsas unit recording elements that are separated in both the radialdirection and the direction of rotation of the information recordingmedium by concave parts in the concave/convex pattern are disposedconcentrically or in a spiral. Also, the expression “unit convex partlength” in this specification refers to a reference length for detectingthat “one convex part is present” when reading a magnetic signal from aninformation recording medium. Accordingly, on an actual informationrecording medium, in accordance with the content of the servo data, theservo pattern is composed of convex parts of a length that is an integermultiple of the unit convex part length. Here, the reference length fordetecting that “one concave part is present” may be set at a commonlength for the entire servo pattern or may be set at different lengthsfor the different types of pattern (preamble pattern, address pattern,burst pattern, and the like) that construct the servo pattern. Inaddition, normally the formation position of a convex part is detectedas “output present for a detection signal” or “a high signal level for adetection signal”.

According to the above information recording medium, by forming theconcave/convex pattern that constructs the servo pattern by setting theunit convex part length so that a value produced by dividing the unitconvex part length by a distance from a center of the data track patterndecreases from an inner periphery to an outer periphery, compared to aconventional information recording medium (the magnetic disk 10 x) wherea concave/convex pattern is formed so that the unit convex part lengthalong the direction of rotation increases in proportion to the distancefrom the center of the data track pattern (so that the value produced bydividing the unit convex part length by the distance from the center isequal across the entire range from the inner periphery to the outerperiphery), it is possible to sufficiently reduce the unit convex partlength in the outer periphery. Accordingly, when etching a layer ofnon-magnetic material formed so as to cover the respective convex parts,it is possible to avoid a situation where there is a large differencebetween the thickness of the residual on the respective convex parts inthe outer periphery and the thickness of the residual on the respectiveconvex parts in the inner periphery. Also, when the non-magneticmaterial is etched so that there is no non-magnetic material (residual)on the respective convex parts across the entire range from the innerperiphery to the outer periphery, it is possible to remove the residualon the respective convex parts without causing a situation where in theinner periphery, the convex parts (the magnetic material) themselves areetched together with the non-magnetic material. By doing so, it ispossible to maintain favorable smoothness for the information recordingmedium across the entire range from the inner periphery to the outerperiphery. For this reason, the flying height of a magnetic head abovethe information recording medium can be kept equal across the entirerange from the inner periphery to the outer periphery of the informationrecording medium, and therefore stable recording and reproducing can becarried out by a recording/reproducing apparatus equipped with thisinformation recording medium.

Also, on an information recording medium according to the presentinvention, in the concave/convex pattern that constructs the servopattern, a unit concave part length may be set so that a value producedby dividing the unit concave part length by a distance from the centerof the data track pattern decreases from the inner periphery to theouter periphery.

It should be noted that the expression “unit concave part length” inthis specification refers to a reference length for detecting that “oneconcave part is present” when reading a magnetic signal from aninformation recording medium. Accordingly, on an actual informationrecording medium, in accordance with the content of the servo data, theservo pattern is composed of concave parts of a length that is aninteger multiple of the unit concave part length. Here, the referencelength for detecting that “one concave part is present” may be set at acommon length for the entire servo pattern or may be set at differentlengths for the different types of pattern (preamble pattern, addresspattern, burst pattern, and the like) that construct the servo pattern.In addition, normally the formation position of a concave part isdetected as “no output for a detection signal” or “a low signal levelfor a detection signal”.

According to the above information recording medium, by forming theconcave/convex pattern that constructs the servo pattern by setting theunit concave part length so that the value produced by dividing the unitconcave part length by the distance from the center of the data trackpattern decreases from the inner periphery to the outer periphery,compared to the conventional information recording medium (magnetic disk10 x) where the concave/convex pattern is formed so that the unitconcave part length along the direction of rotation increases inproportion to the distance from the center O (so that the value producedby dividing the unit concave part length by the distance from the centerO is equal across the entire range from the inner periphery to the outerperiphery), the unit concave part length in the outer periphery can besufficiently reduced. Accordingly, since the non-magnetic material canbe etched without causing the situation where the etching of thenon-magnetic material on the convex parts proceeds slowly due to thepresence of concave parts with a long unit concave part length along thedirection of rotation, a situation where there is a large differencebetween the thickness of the residual on the convex parts in the outerperiphery and the thickness of the residual on the convex parts in theinner periphery can be avoided. Also, when the non-magnetic material isetched so that no non-magnetic material (residual) is present on therespective convex parts across the entire range from the inner peripheryto the outer periphery, it is possible to remove the residual on therespective convex parts without causing a situation where in the innerperiphery, the convex parts (the magnetic material) themselves areetched together with the non-magnetic material. By doing so, it ispossible to keep the smoothness of the information recording medium evenmore uniform across the entire range from the inner periphery to theouter periphery.

In addition, on an information recording medium according to the presentinvention, in the concave/convex pattern that constructs the servopattern, the unit convex part length may be set at an equal orsubstantially equal length in an entire range from the inner peripheryto the outer periphery.

It should be noted that for the present invention, even if extremelysmall manufacturing errors occur and there are slight fluctuations inthe unit convex part length in the concave/convex pattern, such lengthsare still included within the concept of “an equal length” (lengths in apredetermined range centered on a predetermined length that is thetarget for manufacturing). The expression “a substantially equal length”includes lengths in a tolerated range of a narrow width set in advance,the range being centered on a predetermined length that is the targetfor manufacturing and not relating to manufacturing errors.

According to the information recording medium, by forming theconcave/convex pattern that constructs the servo pattern by setting theunit convex part length at an equal or substantially equal length acrossan entire range from the inner periphery to the outer periphery, it ispossible to keep the etching conditions (the etching rate) for thenon-magnetic material formed on the respective convex parts (themagnetic material) uniform across the entire range from the innerperiphery to the outer periphery. Accordingly, the difference betweenthe thickness of the residual on the convex parts in the outer peripheryand the thickness of the residual on the convex parts in the innerperiphery can be sufficiently reduced. Also, when the non-magneticmaterial is etched so as to not leave the non-magnetic material(residual) on the respective convex parts across the entire range fromthe inner periphery to the outer periphery, it is possible to remove theresidual on the respective convex parts while avoiding the situationwhere in the inner periphery, the convex parts (the magnetic material)themselves are etched together with the non-magnetic material.Accordingly, it is possible to improve the smoothness of the magneticdisk and make the smoothness more uniform across the entire range fromthe inner periphery to the outer periphery. As a result, the flyingheight of a magnetic head above the information recording medium can bekept uniform across the entire range from the inner periphery to theouter periphery.

In addition, on an information recording medium according to the presentinvention, in the concave/convex pattern that constructs the servopattern, the unit concave part length may be set at an equal orsubstantially equal length in an entire range from the inner peripheryto the outer periphery.

It should be noted that for the present invention, even if extremelysmall manufacturing errors occur and there are slight fluctuations inthe unit concave part length in the concave/convex pattern, such lengthsare still included within the concept of “an equal length” (lengths in apredetermined range centered on a predetermined length that is thetarget for manufacturing).

According to the information recording medium and therecording/reproducing apparatus, by forming the concave/convex patternby setting the unit concave part length at an equal or substantiallyequal length across an entire range from the inner periphery to theouter periphery, it is possible to keep the etching conditions (theetching rate) for the non-magnetic material formed on the respectiveconvex parts (the magnetic material) uniform across an entire range fromthe inner periphery to the outer periphery. Accordingly, the differencebetween the thickness of the residual on the convex parts in the outerperiphery and the thickness of the residual on the convex parts in theinner periphery can be sufficiently reduced. Also, when the non-magneticmaterial is etched so as to not leave the non-magnetic material(residual) on the respective convex parts across the entire range fromthe inner periphery to the outer periphery, it is possible to remove theresidual on the respective convex parts while avoiding the situationwhere in the inner periphery, the convex parts (the magnetic material)themselves are etched together with the non-magnetic material.Accordingly, it is possible to improve the smoothness of the magneticdisk and make the smoothness more uniform across the entire range fromthe inner periphery to the outer periphery. As a result, the flyingheight of a magnetic head above the information recording medium can bekept uniform across the entire range from the inner periphery to theouter periphery.

A recording/reproducing apparatus according to the present inventionincludes any of the information recording media described above and acontrol unit that carries out servo control by reading servo datacorresponding to the servo pattern from the information recording mediumbased on read frequency information (frequency information that is areference for a clock used when detecting (reading) the servo pattern)set in advance in accordance with a distance from a center of the datatrack pattern.

According to the above recording/reproducing apparatus, by having thecontrol unit read servo data corresponding to the servo pattern from theinformation recording medium based on read frequency information set inadvance in accordance with the distance from the center of the datatrack pattern, it is possible to reliably read the servo pattern (theservo data) while rotating the information recording medium at a fixedangular velocity.

Another recording/reproducing apparatus according to the presentinvention includes any of the information recording media describedabove and a control unit that carries out servo control by reading servodata corresponding to the servo pattern from the information recordingmedium based on read frequency information set in advance for each of aplurality of ring-shaped regions produced by concentrically dividing arange from the inner periphery to the outer periphery.

According to the recording/reproducing apparatus described above, byhaving the control unit read the servo data corresponding to the servopattern from the information recording medium based on the readfrequency information set in advance for each of a plurality ofring-shaped regions produced by concentrically dividing a range from theinner periphery to the outer periphery, fewer frequencies for the readfrequency information are sufficient, and therefore it is possible toreduce the number of frequency switching processes for the readfrequency information when a magnetic head carries out a seek operationtoward the inner or outer periphery, for example. By doing so, it ispossible to carry out seek operations in a short time, and thereforedata can be accessed at high speed.

On a stamper according to the present invention, a concave/convexpattern is formed including convex parts formed corresponding to concaveparts in the concave/convex pattern of any of the information recordingmedia described above and concave parts formed corresponding to convexparts in the concave/convex pattern of the information recording media.

According to the above stamper, by forming the concave/convex patternwith convex parts formed corresponding to the concave parts in theconcave/convex pattern of any of the information recording mediadescribed above and concave parts formed corresponding to the convexparts in the concave/convex pattern of such information recordingmedium, unlike for example a method of manufacturing that forms theconcave/convex pattern for use during etching (a concave/convex patternused as a mask when etching to form the servo pattern and the like) byusing an electron beam lithography apparatus to draw an exposure patternin a resin layer of a preform for manufacturing an information recordingmedium and then developing the exposure pattern, it is possible toeasily and quickly form the concave/convex pattern for use duringetching by merely pressing the concave/convex pattern of the stamperinto the resin layer. It is also possible to form the concave/convexpattern for use during etching in a large number of preforms using asingle stamper. Accordingly, the manufacturing cost of the informationrecording medium can be sufficiently reduced.

It should be noted that the disclosure of the present invention relatesto a content of Japanese Patent Application 2004-253749 that was filedon 1 Sep. 2004 and of Japanese Patent Application 2005-142081 that wasfiled on 16 May 2005, the entire content of which is herein incorporatedby reference.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will beexplained in more detail below with reference to the attached drawings,wherein:

FIG. 1 is a block diagram showing the construction of a hard disk drive;

FIG. 2 is a cross-sectional view showing the multilayer structure of amagnetic disk;

FIG. 3 is a plan view of the magnetic disk;

FIG. 4 is a plan view of an inner periphery region of the magnetic disk;

FIG. 5 is a cross-sectional view of an inner periphery servo patternregion in the inner periphery region;

FIG. 6 is a plan view of an outer periphery region of the magnetic disk;

FIG. 7 is a cross-sectional view of an outer periphery servo patternregion in the outer periphery region;

FIG. 8 is a cross-sectional view of a preform for manufacturing themagnetic disk;

FIG. 9 is a cross-sectional view of the preform in a state where anexposure pattern has been drawn on a resin layer by irradiation with anelectron beam;

FIG. 10 is a cross-sectional view of the preform where the resin layerin the state shown in FIG. 9 has been developed or where aconcave/convex pattern of a stamper has been transferred to the resinlayer;

FIG. 11 is a cross-sectional view of the preform in a state where an Simask layer has been etched with a concave/convex pattern as a mask toform a concave/convex pattern (Si mask) on a C mask layer;

FIG. 12 is a cross-sectional view of the preform in a state where the Cmask layer has been etched with the concave/convex pattern as a mask toform a concave/convex pattern (C mask) on a magnetic layer;

FIG. 13 is a cross-sectional view of the preform in a state where themagnetic layer has been etched with the concave/convex pattern as a maskto form a concave/convex pattern on an intermediate layer;

FIG. 14 is a cross-sectional view of the preform and the stamper in astate where the concave/convex pattern of the stamper has been pressedinto the resin layer (the convex parts have been pressed into the resinlayer);

FIG. 15 is a plan view showing examples of ring-shaped regions;

FIG. 16 is a cross-sectional view showing the multilayer structure ofanother magnetic disk;

FIG. 17 is a cross-sectional view showing the multilayer structure ofyet another magnetic disk;

FIG. 18 is a plan view of a conventional magnetic disk;

FIG. 19 is a plan view of an inner periphery region of the conventionalmagnetic disk;

FIG. 20 is a cross-sectional view of an inner periphery servo patternregion in the inner periphery region of the conventional magnetic disk;

FIG. 21 is a plan view of an outer periphery region of the conventionalmagnetic disk; and

FIG. 22 is a cross-sectional view of an outer periphery servo patternregion in the outer periphery region of the conventional magnetic disk.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of an information recording medium, arecording/reproducing apparatus, and a stamper according to the presentinvention will now be described with reference to the attached drawings.

A hard disk drive 1 shown in FIG. 1 is a magnetic recording/reproducingapparatus as one example of a recording/reproducing apparatus accordingto the present invention and includes a spindle motor 2, a magnetic head3, a signal converting unit 4, a detection clock output unit 5, a servodata detecting unit 6, a driver 7, a control unit 8, a ROM 9, and amagnetic disk 10. Here, as one example, the magnetic disk 10 is adiscrete track-type magnetic disk (patterned medium) on which recordingdata can be recorded by perpendicular recording, and corresponds to theinformation recording medium according to the present invention. Morespecifically, as shown in FIG. 2, the magnetic disk 10 is constructed sothat a soft magnetic layer 12, an intermediate layer 13, and a magneticlayer 14 are formed in that order on a glass substrate 11. Here, themagnetic layer 14 formed on the intermediate layer 13 constructs apredetermined concave/convex pattern 20 by having convex parts 21 formedof a magnetic material and concave parts 22 alternately formed. Theconcave parts 22 are filled with a non-magnetic material 15 such asSiO₂. In addition, a thin film of diamond-like carbon (DLC), as oneexample, is formed by chemical vapor deposition (CVD) to produce aprotective layer (DLC layer) 16 with a thickness of around 2 nm on thenon-magnetic material 15 that fills the concave parts 22 and on theconvex parts 21. A lubricant (as one example, a fluoride lubricant) isalso applied onto the surface of the protective layer 16 of the magneticdisk 10.

The glass substrate 11 corresponds to a “substrate” for the presentinvention and is formed with a thickness of around 0.6 mm by polishingthe surface of a glass plate with a diameter of 2.5 inches until thesurface roughness Ra is around 0.2 to 0.3 nm. It should be noted thatthe substrate for the present invention is not limited to a substrate ofa glass material and it is possible to form the substrate of varioustypes of non-magnetic material such as aluminum and ceramics. The softmagnetic layer 12 is formed with a thickness of around 100 nm to 200 nmby sputtering a soft magnetic material such as CoZrNb alloy. Theintermediate layer 13 functions as an underlayer for forming themagnetic layer 14 and is formed with a thickness of around 40 nm bysputtering an intermediate layer forming material such as Cr or anon-magnetic CoCr alloy. The magnetic layer 14 is a layer composed ofthe convex parts 21 formed of the magnetic material. As described later,the convex parts 21 (the concave/convex pattern 20) are formed bycarrying out a process that sputters a CoCrPt alloy, for example, and aprocess that forms the concave parts 22 by etching using a resistpattern or the like as a mask in that order.

In this case, as shown in FIG. 3, on the magnetic disk 10, servo patternregions As are provided between track regions At, with the track regionsAt and the servo pattern regions As being alternately disposed in thedirection of rotation (the direction of the arrow R) of the magneticdisk 10. Also, as shown in FIGS. 4 and 6, a concave/convex pattern 20 tis formed as a data track pattern in the track pattern region At (aninner periphery track pattern region Ati and an outer periphery trackpattern region Ato). Here, the concave/convex pattern 20 t is composedof a plurality of concentric convex parts 21 t (data recording tracks:also referred to hereinafter as “recording tracks”) whose center O (seeFIG. 3) is the center of rotation of the magnetic disk 10 and concaveparts 22 t present between the respective convex parts 21 t. It shouldbe noted that although it is preferable for the center O of theconcave/convex pattern 20 t to match the center of rotation of themagnetic disk 10, in reality, there are cases where an extremely smalldisplacement of around 30 to 50 μm is produced due to manufacturingerror. However, since tracking servo control can still be performedsufficiently for the magnetic head 3 when a displacement of suchmagnitude is present, the center of rotation and the center O can bethought of as effectively matching. Also, the concave parts 22 t of theconcave/convex pattern 20 t are filled with the non-magnetic material 15to make the surface of the track pattern region At smooth.

Also, as shown by FIGS. 4 to 7, a concave/convex pattern 20 s is formedas a servo pattern in the servo pattern region As (an inner peripheryservo pattern region Asi and an outer periphery servo pattern regionAso). Here, the concave/convex pattern 20 s is composed of convex parts21 s (convex parts 21 si and convex parts 21 so) that construct varioustypes of servo patterns such as a preamble pattern, an address pattern,and a burst pattern, and concave parts 22 s (concave parts 22 si andconcave parts 22 so). Also, on the magnetic disk 10, the respectiveconvex parts 21 s are formed so that the length of the convex parts 21 salong the direction of rotation (the direction of the arrow R in thedrawings) is equal across the entire range from the inner periphery tothe outer periphery of the magnetic disk 10 without being proportionalto the distance from the center O of the concave/convex pattern 20 t(i.e., the length does not increase toward the outer periphery). This isone example where a value produced by dividing the unit convex partlength by the distance from the center O of the data track patterndecreases from the inner periphery to the outer periphery as one exampleof where “the unit convex part length is set at an equal orsubstantially equal length” for the present invention.

In the same way, the respective concave parts 22 s are formed so thatthe length of the concave parts 22 s along the direction of rotation(the direction of the arrow R in the drawings) is not equal across theentire range from the inner periphery to the outer periphery of themagnetic disk 10 without being proportional to the distance from thecenter O of the concave/convex pattern 20 t (i.e., the length does notincrease toward the outer periphery). This is one example where a valueproduced by dividing the unit concave part length by the distance fromthe center O of the data track pattern decreases from the innerperiphery to the outer periphery as one example of where “the unitconcave part length is set at an equal or substantially equal length”for the present invention. For this reason, on the magnetic disk 10, thecombined length of the length of a convex part 21 s and the length of aconcave part 22 s along the direction of rotation, or in other words,the formation pitch of a convex part 21 s and a concave part 22 s, isset so as to be equal across the entire range from the inner peripheryto the outer periphery of the magnetic disk 10 without beingproportional to the distance from the center O of the concave/convexpattern 20 t (i.e., without increasing toward the outer periphery).Accordingly, the concave/convex pattern 20 is formed so that the ratioof the length of the convex parts 21 s to the length of the concaveparts 22 s along the direction of rotation is equal across the entirerange from the inner periphery to the outer periphery.

More specifically, as shown in FIGS. 4 and 5, in an inner peripheryregion Ai (as one example, a preamble pattern formation region at aposition 11 mm from the center O of the concave/convex pattern 20 t), alength L3 i that is the total of a length L2 i of a concave part 22 si(as one example, 220 nm) and a length L1 i of a convex part 21 si (asone example, 220 nm) is set at 440 nm. On the other hand, as shown inFIGS. 6 and 7, in an outer periphery region Ao (as one example, apreamble pattern formation region at a position 32 mm from the center Oof the concave/convex pattern 20 t), a length L3 o that is the total ofa length L2 o of a concave part 22 so (as one example, 220 nm which isequal to the length L1 o of the convex part 21 so) and a length L1 o ofa convex part 21 so (as one example, at 220 nm which is equal to thelength L1 i of the convex part 21 si) is set at 440 nm. As a result, asshown in FIGS. 5 and 7, on the magnetic disk 10, the ratio of the lengthL1 i of a convex part 21 si to the length L2 i of a concave part 22 siin the concave/convex pattern 20 s in the inner periphery region Ai andthe ratio of the length L1 o of a convex part 21 so to the length L2 oof a concave part 22 so in the outer periphery region Ao arerespectively 1:1 (the ratio of the unit convex part length to the unitconcave part length is 1).

In this case, the ratio of the length of a convex part 21 s (the unitconvex part length) to the length of a concave part 22 s (the unitconcave part length) is set in the same way not only for the preamblepattern mentioned above but also for the concave/convex pattern 20 sthat constructs the address pattern and the burst pattern. Regarding theburst pattern, in a region where a plurality of oblong convex parts 21 sare disposed in lines on both sides on the concave parts 22 s along thedirection of rotation of the magnetic disk 10, the ratio of the unitconvex part length to the unit concave part length is set so that theabove conditions are satisfied. It should be noted that in FIGS. 4 to 7,the preamble pattern and burst pattern in the servo pattern areschematically illustrated and for ease of understanding, the lengths ofthe respective convex parts 21 s and the respective concave parts 22 salong the direction of rotation are illustrated using the unit convexpart length and unit concave part length of the servo pattern only.Accordingly, on actual magnetic disks 10, the number, formationpositions, and lengths of the convex parts 21 s and the concave parts 22s differ to the states shown in the respective drawings, and theconcave/convex pattern 20 s is formed with the number, formationpositions, and lengths of the convex parts 21 s and the concave parts 22s corresponding to the various types of control data includinginformation (patterns) such as track addresses and sector addressesrequired for tracking servo control. In this case, the actual lengths ofthe convex parts 21 s and the concave parts 22 s are integer multiplesof the lengths of the convex parts 21 s and the concave parts 22 s(i.e., integer multiples of the unit convex part length and the unitconcave part length).

The spindle motor 2 rotates the magnetic disk 10 at a fixed rotationalspeed, such as 4200 rpm, under the control of the control unit 8. Asshown in FIG. 1, the magnetic head 3 is attached to an actuator 3 b viaa swing arm 3 a and is moved above the magnetic disk 10 during therecording and reproducing of recording data on the magnetic disk 10.Also, the magnetic head 3 carries out reads of servo data from the servopattern region As of the magnetic disk 10, magnetic writes of recordingdata in the track pattern region At (the convex parts 21 t), and readsof recording data that has been magnetically written in the trackpattern region At. It should be noted that although an actual magnetichead 3 is formed on a base surface (air bearing surface) of a sliderthat causes the magnetic head 3 to fly above the magnetic disk 10, theslider has been omitted from this specification and the drawings. Theactuator 3 b swings the swing arm 3 a by a driving current supplied fromthe driver 7 under the control of the control unit 8 and thereby movesthe magnetic head 3 to an arbitrary recording/reproducing position abovethe magnetic disk 10. The signal converting unit 4 includes anamplifier, a low pass filter (LPF), an A/D converter, and the like (notshown), amplifies various signals obtained by the magnetic head 3 fromthe magnetic disk 10, removes noise, and then carries out an A/Dconversion and outputs digital data.

The ROM 9 stores clock data Dc1 for read frequency information to beoutputted by the control unit 8 associated with a movement position (adistance from the center O) of the magnetic head 3. Here, as describedlater, based on the clock data Dc1, the control unit 8 linearly convertsthe frequency of the read frequency information so that the wavelengthdecreases toward the outer periphery in proportion to the distance fromthe center O of the concave/convex pattern 20 t and outputs the readfrequency information to the detection clock output unit 5. Thedetection clock output unit 5 obtains the read frequency informationoutputted by the control unit 8 based on the clock data Dc1 and obtains(detects), out of the digital data outputted from the signal convertingunit 4, data (a signal) of a preamble read via the magnetic head 3 fromthe servo pattern region As. In addition, based on the read frequencyinformation and the preamble data, the detection clock output unit 5adjusts the phase, frequency, and the like to generate and output adetection clock signal Cls used when actually detecting the servo data.

In this case, on the magnetic disk 10, since the concave/convex pattern20 s is formed so that the length of the servo pattern region As alongthe direction of rotation is equal across the entire range from theinner periphery to the outer periphery, when the magnetic disk 10 isrotated at a fixed angular velocity, the time that the servo patternregion As passes below the magnetic head 3 decreases toward the outerperiphery. Accordingly, in a state where the magnetic disk 10 is rotatedat a fixed velocity of 4200 rpm, for example, when the magnetic head 3is kept aligned with a recording track (convex parts 21 t) in the innerperiphery region Ai, the control unit 8 outputs read frequencyinformation of 22 MHz and when the magnetic head 3 is kept aligned witha recording track (convex parts 21 t) in the outer periphery region Ao,the control unit 8 outputs read frequency information of 64 MHz. Also,when the magnetic head 3 is kept aligned with any recording track(convex parts 21 t) from the inner periphery region Ai to the outerperiphery region Ao, the control unit 8 linearly changes the readfrequency information in a range of 22 MHz to 64 MHz in proportion tothe distance from the center O of the concave/convex pattern 20 t.

The servo data detecting unit 6 reads in synchronization with thedetection clock Cls outputted from the detection clock output unit 5 toobtain (detect) servo data Ds from the digital data outputted from thesignal converting unit 4 and outputs the servo data Ds to the controlunit 8. The driver 7 controls the actuator 3 b in accordance with acontrol signal from the control unit 8 so that the magnetic head 3 iskept aligned with a desired recording track (the convex parts 21 t). Thecontrol unit 8 carries out overall control of the hard disk drive 1. Thecontrol unit 8 specifies, based on head position information outputtedfrom the servo data detecting unit 6, on which recording track in arange from the inner periphery to the outer periphery on the magneticdisk 10 the magnetic head 3 is aligned, converts the read frequencyinformation as described above in accordance with the clock data Dc1(data on frequency converting conditions) stored in the ROM 9 and inaccordance with the desired position of the magnetic head 3 (theposition of a recording track to which the magnetic head 3 is to move),and outputs the read frequency information to the detection clock outputunit 5. The control unit 8 also controls the driver 7 based on the servodata Ds outputted from the servo data detecting unit 6.

Next, the method of manufacturing the magnetic disk 10 will be describedwith reference to the drawings.

First, after the soft magnetic layer 12 has been formed by sputteringCoZrNb alloy on the glass substrate 11, the intermediate layer 13 isformed by sputtering an intermediate layer forming material on the softmagnetic layer 12. Next, by sputtering CoCrPt alloy on the intermediatelayer 13, the magnetic layer 14 is formed with a thickness of around 15nm. After this, a C (carbon) mask layer 17 is formed on the magneticlayer 14 with a thickness of around 12 nm by sputtering, for example,and an Si mask layer 18 is formed on the C mask layer 17 with athickness of around 4 nm by sputtering. Next, a positive-type electronbeam resist is spin-coated on the Si mask layer 18 to form a resin layer19 (mask forming functional layer) with a thickness of around 130 nm. Bydoing so, as shown in FIG. 8, a preform 30 for manufacturing themagnetic disk 10 is completed. Next, as shown in FIG. 9, an electronbeam EB is emitted onto the preform 30 using an electron beamlithography apparatus to draw an exposure pattern with the same planarshape as the concave/convex pattern 20 s and the concave/convex pattern20 t on the resin layer 19. After this, by developing the resin layer 19on which the drawing of the exposure pattern has been completed, asshown in FIG. 10, a concave/convex pattern 41 (resist pattern) is formedon the Si mask layer 18.

Next, by carrying out ion beam etching with argon (Ar) gas using theconcave/convex pattern 41 (the resin layer 19) as a mask, the Si masklayer 18 exposed by the mask (convex parts 41 a) at the bottoms of theconcave parts 41 b in the concave/convex pattern 41 is etched to form aconcave/convex pattern 42 (Si mask pattern) in the Si mask layer 18 asshown in FIG. 11. After this, reactive ion etching is carried out withoxygen gas as the reactive gas and the concave/convex pattern 42 as amask to etch the C mask layer 17 exposed from the mask (convex parts 42a) at the bottoms of the concave parts 42 b in the concave/convexpattern 42 to form a concave/convex pattern 43 (C mask pattern) in the Cmask layer 17 as shown in FIG. 12. Next, ion beam etching is carried outusing argon (Ar) gas and the concave/convex pattern 43 as a mask. Bydoing so, as shown in FIG. 13, the positions in the magnetic layer 14that were covered by the mask pattern (positions covered by convex parts43 a of the concave/convex pattern 43) become the convex parts 21 andpositions exposed from the mask pattern (positions that were exposed atthe bottoms of concave parts 43 b of the concave/convex pattern 43)become the concave parts 22, thereby forming the concave/convex pattern20 (the concave/convex patterns 20 s and 20 t) on the intermediate layer13. Next, by carrying out reactive ion etching of the C mask layer 17(the C mask pattern) remaining on the convex parts 21 with oxygen gas asthe reactive gas, the upper surfaces of the convex parts 21 are exposed(the remaining C mask layer 17 is removed).

Next, while a bias power of around 150 W for example is applied to thepreform 30, SiO₂ as the non-magnetic material 15 is sputtered with thepressure of the argon (Ar) gas set at 0.3 Pa, for example. At this time,a sufficient amount of the non-magnetic material 15 is sputtered tocompletely fill the concave parts 22 with the non-magnetic material 15and form a layer of non-magnetic material 15 with a thickness of around60 nm, for example, on the upper surfaces of the convex parts 21. Here,by sputtering the non-magnetic material 15 in a state where bias poweris applied to the preform 30, a layer of non-magnetic material 15 isformed without producing large convexes and concaves on the surface.Next, ion beam etching is carried out on the layer of the non-magneticmaterial 15 on the magnetic layer 14 (on the convex parts 21, on theconcave parts 22, and inside the concave parts 22) in a state where thepressure of the argon (Ar) gas is set at 0.04 Pa, for example, and wherethe incident angle of the ion beam on the surface of the preform 30 (thelayer of the non-magnetic material 15) is set at 2°. At this time, theion beam etching continues until the upper surfaces of the respectiveconvex parts 21 si in the inner periphery (the position that will laterbecome the inner periphery region Ai) of the preform 30 are exposed fromthe non-magnetic material 15.

Here, on the magnetic disk 10 (the preform 30), the length L1 i of theconvex parts 21 si in the inner periphery and the length L1 o of theconvex parts 21 so in the outer periphery are formed at an equal length(in this example, 220 nm). Accordingly, by carrying out the ion beametching process until the upper surfaces of the respective convex parts21 si are exposed in the inner periphery, the upper surfaces of therespective convex parts 21 so in the outer periphery are also exposed(the upper surfaces of the convex parts 21 si, 21 so are exposed atsubstantially the same time). By doing so, the ion beam etching of thenon-magnetic material 15 is completed and the surface of the preform 30is made smooth. Next, after the protective layer 16 has been formed byforming a thin film of diamond-like carbon (DLC) by CVD so as to coverthe surface of the preform 30, a fluoride lubricant is applied to thesurface of the protective layer 16 so that the average thickness isaround 2 nm, for example. By doing so, the magnetic disk 10 is completedas shown in FIG. 2.

On the magnetic disk 10, as described above, the respective convex parts21 s and the respective concave parts 22 s are formed so that the length(lengths L1 i, L1 o) of the convex parts 21 s along the direction ofrotation of the concave/convex pattern 20 s of the servo pattern regionAs and the length (lengths L2 i, L2 o) of the concave parts 22 s alongthe direction are equal across the entire range from the inner peripheryto the outer periphery of the magnetic disk 10, so that as shown inFIGS. 5 and 7, across the entire range of the magnetic disk 10, thenon-magnetic material 15 (residual) on the respective convex parts 21 sis removed. Accordingly, the height difference H between the convexesand concaves in the surface of the magnetic disk 10 is uniform acrossthe entire range of the magnetic disk 10. More specifically, the degreeof unevenness, that is, the surface roughness Ra of the surface of themagnetic disk 10 in both the inner periphery region Ai and the outerperiphery region Ao is around 0.7 nm. Accordingly, the flying height ofthe magnetic head 3 (the slider) becomes substantially constant acrossthe entire region from the inner periphery of the magnetic disk 10 tothe outer periphery, and therefore stabilized recording and reproducingbecome possible.

On the other hand, on the magnetic disk 10 x manufactured according tothe conventional method of manufacturing, the surface roughness Ra ofthe magnetic disk 10 x in the inner periphery region Axi is around 0.7nm in a state where the upper surface of the convex parts 21 sxi areexposed from the non-magnetic material 15 in the inner periphery regionAxi where the length L1 xi along the direction of rotation iscomparatively short. On the other hand, the surface roughness Ra of themagnetic disk 10 x in the inner periphery region Axo where the length L1xo along the direction of rotation becomes longer than in the innerperiphery region Axi in proportion to the distance from the center O ofthe concave/convex pattern 20 t is around 3.1 nm due to the thickness ofthe residual on the convex parts 21 sxo being thicker. In this case,when the non-magnetic material 15 is etched with etching conditions thatexpose the upper surfaces of the convex parts 21 sxo from thenon-magnetic material 15 in the outer periphery region Axo, the etchingof the non-magnetic material 15 proceeds inside the concave parts 22 sxacross the entire range from the inner periphery of the magnetic disk 10x to the outer periphery, thereby causing deterioration in thesmoothness of the magnetic disk 10 x. In addition, when the non-magneticmaterial 15 is etched with the etching conditions described above, theconvex parts 21 sxi in the inner periphery region Axi are excessivelyetched, resulting in the risk of it being difficult to read a magneticsignal properly. For this reason, on the magnetic disk 10 x manufacturedaccording to the conventional method of manufacturing, it is difficultto make it possible to read the servo data Ds properly while making theflying height of the magnetic head 3 (slider) uniform across the entireregion from the inner periphery of the magnetic disk 10 x to the outerperiphery.

In addition, on the magnetic disk 10, as described above, the respectiveconvex parts 21 s and the respective concave parts 22 s are formed sothat the combined length (lengths L3 i, L3 o) of the length of theconvex parts 21 s and the length of the concave parts 22 s along thedirection of rotation in the concave/convex pattern 20 s of servopattern As is equal across the entire range from the inner periphery tothe outer periphery of the magnetic disk 10. Accordingly, as shown inFIG. 3, the length L4 i along the direction of rotation of the innerperiphery servo pattern region Asi (the concave/convex pattern 20 s inthe inner periphery) and the length L4 o along the direction of rotationof the outer periphery servo pattern region Aso (the concave/convexpattern 20 s in the outer periphery) are equal. For this reason, on themagnetic disk 10, the length along the direction of rotation of thetrack pattern region At gradually increases from the inner periphery tothe outer periphery. More specifically, the length L5 o along thedirection of rotation of the outer periphery track pattern region Ato(the concave/convex pattern 20 t in the outer periphery) is longer thanthe length L5 i along the direction of rotation of the inner peripherytrack pattern region Ati (the concave/convex pattern 20 t in the innerperiphery). Accordingly, compared to the conventional magnetic disk 10x, the capacity for recording data is increased by an amount equivalentto the increase in the length of the convex parts 21 t in the outerperiphery.

In this way, according to the magnetic disk 10 and the hard disk drive1, by forming the concave/convex pattern 20 s (the servo pattern) bysetting the unit convex part length so that the value produced bydividing the unit convex part length by the distance from the center Oof the concave/convex pattern 20 t decreases from the inner periphery tothe outer periphery, compared to the conventional magnetic disk 10 xwhere the concave/convex pattern is formed so that the unit convex partlength increases in proportion to the distance from the center O (sothat the value produced by dividing the unit convex part length by thedistance from the center O of the concave/convex pattern 20 t is equalacross the entire range from the inner periphery to the outerperiphery), the unit convex part length in the outer periphery can besufficiently reduced. Accordingly, when a layer of the non-magneticmaterial 15 formed so as to cover the respective convex parts 21 isetched, it is possible to avoid the situation where there is a largedifference between the thickness of the residual on the convex parts 21so in the outer periphery and the thickness of the residual on theconvex parts 21 si in the inner periphery. In addition, when thenon-magnetic material 15 is etched so that the non-magnetic material 15(residual) is not present on the respective convex parts 21 s in theentire range from the inner periphery to the outer periphery, it ispossible to remove the residual on the respective convex parts 21 swithout the risk of a situation where in the inner periphery, the convexparts 21 s (magnetic material) themselves are etched together with thenon-magnetic material 15. By doing so, it is possible to maintainfavorable smoothness for the magnetic disk 10 across the entire rangefrom the inner periphery to the outer periphery. Since it is possible tokeep the flying height of the magnetic head 3 above the magnetic disk 10substantially equal across the entire range from the inner periphery ofthe magnetic disk 10 to the outer periphery, the hard disk drive 1 cancarry out recording and reproducing stably.

Also, according to the magnetic disk 10 and the hard disk drive 1, byforming the concave/convex pattern 20 s (servo pattern) with the unitconcave part length set so that the value produced by dividing the unitconcave part length by the distance from the center O of theconcave/convex pattern 20 t decreases from the inner periphery to theouter periphery, compared to the conventional magnetic disk 10 x wherethe concave/convex pattern is formed so that the unit concave partlength along the direction of rotation increases in proportion to thedistance from the center O (so that the value produced by dividing theunit concave part length by the distance from the center O is equalacross the entire range from the inner periphery to the outerperiphery), the unit concave part length in the outer periphery can besufficiently reduced. Accordingly, since it is possible to etch thelayer of the non-magnetic material 15 without the etching of thenon-magnetic material 15 on the convex parts 21 s slowing due to thepresence of concave parts with a long unit concave part length along thedirection of rotation, the situation where there is a large differencebetween the thickness of the residual on the convex parts 21 so in theouter periphery and the thickness of the residual of the convex parts 21si in the inner periphery can be avoided. Also, when the non-magneticmaterial 15 is etched so that there is no non-magnetic material 15(residual) on the respective convex parts 21 s across the entire rangefrom the inner periphery to the outer periphery, it is possible toremove the residual on the respective convex parts 21 s without causinga situation where in the inner periphery, the convex parts 21 s (themagnetic material) themselves are etched together with the non-magneticmaterial 15. By doing so, the smoothness of the magnetic disk 10 can bemaintained more favorably across the entire range from the innerperiphery to the outer periphery.

In addition, according to the magnetic disk 10 and the hard disk drive1, by forming the concave/convex pattern 20 s (the servo pattern) bysetting the unit convex part length at an equal length across the entirerange from the inner periphery to the outer periphery, it is possible tokeep the etching conditions (the etching rate) for the non-magneticmaterial 15 formed on the respective convex parts 21 s (the magneticmaterial) uniform across an entire range from the inner periphery to theouter periphery. Accordingly, the difference between the thickness ofthe residual on the convex parts 21 so in the outer periphery and thethickness of the residual on the convex parts 21 si in the innerperiphery can be sufficiently reduced. Also, when the non-magneticmaterial 15 is etched so as to not leave the non-magnetic material 15(residual) on the respective convex parts 21 s across the entire rangefrom the inner periphery to the outer periphery, it is possible toremove the residual on the respective convex parts 21 s while avoidingthe situation where in the inner periphery, the convex parts 21 s (themagnetic material) themselves are etched together with the non-magneticmaterial 15. Accordingly, it is possible to improve the smoothness ofthe magnetic disk 10 and make the smoothness more uniform across theentire range from the inner periphery to the outer periphery. As aresult, the flying height of the magnetic head 3 above the magnetic disk10 can be kept uniform across the entire range from the inner peripheryto the outer periphery.

Also, according to the magnetic disk 10 and the hard disk drive 1, byforming the concave/convex pattern 20 s (servo pattern) by setting theunit concave part length at an equal length across the entire range fromthe inner periphery to the outer periphery, it is possible to keep theetching conditions (the etching rate) for the non-magnetic material 15formed on the respective convex parts 21 s (the magnetic material)uniform across an entire range from the inner periphery to the outerperiphery. Accordingly, the difference between the thickness of theresidual on the convex parts 21 so in the outer periphery and thethickness of the residual on the convex parts 21 si in the innerperiphery can be sufficiently reduced. Also, when the non-magneticmaterial 15 is etched so as to not leave the non-magnetic material 15(residual) on the respective convex parts 21 s across the entire rangefrom the inner periphery to the outer periphery, it is possible toremove the residual on the respective convex parts 21 s while avoidingthe situation where in the inner periphery, the convex parts 21 s (themagnetic material) themselves are etched together with the non-magneticmaterial 15. Accordingly, it is possible to improve the smoothness ofthe magnetic disk 10 and make the smoothness more uniform across theentire range from the inner periphery to the outer periphery. As aresult, the flying height of the magnetic head 3 above the magnetic disk10 can be kept uniform across the entire range from the inner peripheryto the outer periphery.

Also, according to the hard disk drive 1, by having the servo datadetecting unit 6 read the servo data Ds corresponding to the servopattern from the magnetic disk 10 based on the read frequencyinformation set in advance in accordance with the distance from thecenter O of the concave/convex pattern 20 t, it is possible to reliablyread the servo data Ds from the servo pattern region As while rotatingthe magnetic disk 10 at a fixed angular velocity.

Next, another method of manufacturing the magnetic disk 10 will bedescribed with reference to the drawings. It should be noted thatdetailed description of processes that are the same as in the method ofmanufacturing described above has been omitted.

Although in the method of manufacturing the magnetic disk 10 describedabove, a developing process is carried out after an exposure pattern hasbeen drawn on the resin layer 19 of the preform 30 using an electronbeam lithography apparatus to form the concave/convex pattern 41 (resistpattern) used as a mask for use during etching, the method ofmanufacturing an information recording medium according to the presentinvention is not limited to this. For example, it is possible to formthe concave/convex pattern 41 in the resin layer 19 of the preform 30 byan imprinting method using a stamper 35 (see FIG. 14) as one example ofa stamper according to the present invention. In this case, as shown inFIG. 14, a concave/convex pattern 39 where the positional relationshipof the convexes and concaves is the reverse of the concave/convexpattern 20 (the concave/convex patterns 20 t, 20 s) of the magnetic disk10 is formed in the stamper 35. It should be noted that theconcave/convex pattern 39 of the stamper 35 is formed so that convexparts 39 a correspond to the concave parts 22 in the concave/convexpattern 20 of the magnetic disk 10 and concave parts 39 b correspond tothe convex parts 21 of the concave/convex pattern 20. Accordingly, onthe stamper 35, the length of the convex parts 39 a along the directionof rotation is substantially equal to the length along the direction ofrotation of the concave parts 22 in the concave/convex pattern 20, andthe length of the concave parts 39 b along the direction of rotation issubstantially equal to the length along the direction of rotation of theconvex parts 21 in the concave/convex pattern 20. It should be notedthat there are no particular limitations regarding the method ofmanufacturing the stamper 35, and the stamper 35 can be manufacturedaccording to a variety of known methods.

When the magnetic disk 10 is manufactured using the stamper 35, as shownin FIG. 14, first the concave/convex pattern 39 of the stamper 35 istransferred to the resin layer 19 of the preform 30 by imprinting. Morespecifically, by pressing the surface of the stamper 35 in which theconcave/convex pattern 39 is formed into the resin layer 19 of thepreform 30, the convex parts 39 a of the concave/convex pattern 39 arepressed into the resin layer 19 of the preform 30. Next, the stamper 35is separated from the preform 30 and resin (residual: not shown)remaining in the bottom surfaces are removed by an oxygen plasmaprocess. By doing so, as shown in FIG. 10, the concave/convex pattern 41is formed on the Si mask layer 18 of the preform 30. Next, by etchingthe Si mask layer 18 using the concave/convex pattern 41 as a mask, theconcave/convex pattern 42 is formed on the C mask layer 17, and byetching the C mask layer 17 using the concave/convex pattern 42 as amask, the concave/convex pattern 43 is formed on the magnetic layer 14.After this, the magnetic layer 14 is etched using the concave/convexpattern 43 as a mask to form the concave/convex pattern 20 on theintermediate layer 13. Next, after the non-magnetic material 15 has beensputtered in the same way as the method of manufacturing describedabove, ion beam etching is carried out on the layer of the non-magneticmaterial 15 to make the surface smooth. After this, the protective layer16 is formed by forming a thin film of diamond-like carbon (DLC) usingCVD and a fluoride lubricant is applied onto the surface of theprotective layer 16. By doing so, as shown in FIG. 2, the magnetic disk10 is completed.

In this way, according to the stamper 35 for manufacturing the magneticdisk 10, by forming the concave/convex pattern 39 with the convex parts39 a formed corresponding to the concave parts 22 in the concave/convexpattern 20 (the concave/convex patterns 20 t, 20 s) of the magnetic disk10 and the concave parts 39 b formed corresponding to the convex parts21 in the concave/convex pattern 20 of the magnetic disk 10, unlike forexample a method of manufacturing that forms the concave/convex pattern41 by using an electron beam lithography apparatus to draw an exposurepattern with the same planar shape as the concave/convex patterns 20 s,20 t in the resin layer 19 of the preform 30 and then developing theexposure pattern, it is possible to easily form the concave/convexpattern 41 in a short time by merely pressing the concave/convex pattern39 of the stamper 35 into the resin layer 19. It is also possible toform the concave/convex pattern 41 in a large number of preforms 30using a single stamper 35. Accordingly, the manufacturing cost of themagnetic disk 10 can be sufficiently reduced.

It should be noted that the present invention is not limited to theabove structures. For example, although an example has been describedwhere the concave/convex pattern 20 s is formed so that the lengths (thelengths L1 i, L1 o) of the respective convex parts 21 s along thedirection of rotation are equal across the entire range from the innerperiphery to the outer periphery, the concave/convex pattern 20 s can beformed so that the lengths of the respective convex parts 21 s and thelengths of the respective concave parts 22 s slightly differ atpositions from the inner periphery to the outer periphery. Morespecifically, it is possible to use a structure where the length alongthe direction of rotation of the convex parts 21 so in the outerperiphery is longer than the convex parts 21 si in the inner peripheryand a structure where the length along the direction of rotation of theconcave parts 22 so in the outer periphery is longer than the concaveparts 22 si in the inner periphery. It is also possible to use astructure where the length along the direction of rotation of the convexparts 21 so in the outer periphery is slightly shorter than the convexparts 21 si in the inner periphery and a structure where the lengthalong the direction of rotation of the concave parts 22 so in the outerperiphery is slightly shorter than the concave parts 22 si in the innerperiphery. Even with these structures where the lengths of the convexparts 21 s and/or the concave parts 22 s differ, by forming theconcave/convex pattern 20 s with the unit convex part length set so thatthe length of the convex parts 21 so in the outer periphery is shorterthan the length L1 xo of the convex parts 21 sxo on the conventionalmagnetic disk 10 x, it is possible to form the residual on the convexparts 21 so in the outer periphery sufficiently thinly, and thereforefavorable smoothness can be maintained in the outer periphery of themagnetic disk.

Also, although on the hard disk drive 1 described above, a constructionis used where the control unit 8 specifies the position of the magnetichead 3 (the distance from the center O of the concave/convex pattern 20t) based on a signal from the servo data detecting unit 6, linearlyconverts the frequency of the read frequency information in accordancewith the position to which the magnetic head 3 is to be moved, andoutputs the read frequency information, the present invention is notlimited to this. For example, as shown in FIG. 15, by dividing the rangefrom the inner periphery region Ai to the outer periphery range Ao ofthe magnetic disk 10 into concentric circles to produce a plurality ofring-shaped regions A1, A2 . . . An (where N is a natural number of 2 orabove: such regions are hereinafter referred to the “ring-shaped regionsAM” (where M is a natural number in a range of 2 to M inclusive) when nodistinction is required), it is possible to set the frequency of theread frequency information separately for each of the ring-shapedregions AM. Also, during recording and reproducing, the control unit 8specifies the position of the magnetic head 3 (the ring-shaped regionAM) based on a signal from the servo data detecting unit 6 and outputsread frequency information corresponding to the position (thering-shaped region AM) to which the magnetic head 3 is to be moved tothe detection clock output unit 5. Here, the respective widths of thering-shaped regions A1, A2 . . . AN described above (the lengths alongthe radial direction of the magnetic disk 10) should preferably be setin a range where the servo data Ds is readable based on the readfrequency information with the same frequency, that is, the widthsshould preferably be set in a range where the detection clock outputunit 5 can adjust the phase and frequency based on the read frequencyinformation and the preamble data to generate the detection clock Clsused as a synchronization clock when actually reading the servo data.According to this construction, compared to the hard disk drive 1described above where the control unit 8 linearly converts the frequencyof the read frequency information in accordance with the distance of themagnetic head 3 from the center O of the concave/convex pattern 20 t,fewer frequencies for the read frequency information are sufficient, andtherefore it is possible to reduce the number of frequency switchingprocesses for the read frequency information when the magnetic head 3carries out a seek operation toward the inner or outer periphery, forexample. By doing so, it is possible to carry out seek operations in ashort time, and therefore data can be accessed at high speed.

In addition, although in the hard disk drive 1 described above, thecontrol unit 8 converts the frequency of the read frequency informationoutputted to the detection clock output unit 5 in accordance with thedistance of the magnetic head 3 from the center O of the concave/convexpattern 20 t while the magnetic disk 10 is rotated at a fixed angularvelocity, the present invention is not limited to this and it ispossible to use a construction where the magnetic disk 10 is rotated ata fixed linear rotational velocity and the servo data Ds is read by theservo data detecting unit 6 by having read frequency information of afixed frequency outputted from the control unit 8.

In addition, the servo pattern of the present invention is not limitedto the example described above, and it is possible to form the servopattern by setting the unit convex unit length and the unit concave unitlength so that the concave/convex form of the concave/convex pattern 20s in the servo pattern region As of the magnetic disk 10 is reversed andso that the various conditions for the present invention are satisfied.Also, although the respective convex parts 21 of the concave/convexpattern 20 are formed of magnetic material from the bottom ends to thetop ends on the magnetic disk 10 described above, the present inventionis not limited to this and by forming a magnetic layer 14 a so as tocover a concave/convex pattern formed in the substrate 11 a as in themagnetic disk 10 a shown in FIG. 16, it is possible to construct theconcave/convex pattern 20 a with the convex parts 21 a whose surfacesare formed by the magnetic layer 14 a and the concave parts 22 a whosebottom surfaces are also formed by the magnetic layer 14 a. In thiscase, in the same way as the method of forming the concave/convexpattern 20 on the magnetic disk 10 described above, the concave/convexpattern of the substrate 11 a can be formed by etching the substrate 11a using the concave/convex pattern 43 that was used as a mask whenetching the magnetic layer 14, for example. Also, by press molding orinjection molding using a stamper in the same way as the stamper 35, forexample, it is possible to form a concave/convex pattern in thesubstrate 11 a. In addition, in the same way as the magnetic disk 10 bshown in FIG. 17, it is possible to construct a concave/convex pattern20 b of a continuous magnetic layer 14 b that constructs the respectiveconvex parts 21 b and bottom surfaces of the concave parts 22 b betweenthe respective convex parts 21 b. Also, although the magnetic disks 10,10 a, and 10 b are magnetic disks for perpendicular recording, it isalso possible to apply the present invention to magnetic disks forlongitudinal recording.

1. An information recording medium where a data track pattern and aservo pattern composed of a concave/convex pattern including a pluralityof convex parts are formed on at least one surface of a substrate andrespective concave parts in the concave/convex pattern are filled withnon-magnetic material, wherein in the concave/convex pattern thatconstructs the data track pattern, the respective convex parts areformed concentrically or in a spiral, and in the concave/convex patternthat constructs the servo pattern, a unit convex part length along adirection of rotation of the substrate is set so that a value producedby dividing the unit convex part length by a distance from a center ofthe data track pattern decreases from an inner periphery to an outerperiphery.
 2. An information recording medium according to claim 1,wherein in the concave/convex pattern that constructs the servo pattern,a unit concave part length along the direction of rotation is set sothat a value produced by dividing the unit concave part length by adistance from the center of the data track pattern decreases from theinner periphery to the outer periphery.
 3. An information recordingmedium according to claim 1, wherein in the concave/convex pattern thatconstructs the servo pattern, the unit convex part length is set at anequal or substantially equal length in an entire range from the innerperiphery to the outer periphery.
 4. An information recording mediumaccording to claim 1, wherein in the concave/convex pattern thatconstructs the servo pattern, the unit concave part length is set at anequal or substantially equal length in an entire range from the innerperiphery to the outer periphery.
 5. A recording/reproducing apparatuscomprising an information recording medium according to claim 1 and acontrol unit that carries out servo control by reading servo datacorresponding to the servo pattern from the information recording mediumbased on read frequency information set in advance in accordance withthe distance from a center of the data track pattern.
 6. Arecording/reproducing apparatus comprising an information recordingmedium according to claim 1 and a control unit that carries out servocontrol by reading servo data corresponding to the servo pattern fromthe information recording medium based on read frequency information setin advance for each of a plurality of ring-shaped regions produced byconcentrically dividing a range from the inner periphery to the outerperiphery.
 7. A stamper for manufacturing an information recordingmedium, on which is formed a concave/convex pattern including convexparts formed corresponding to concave parts in the concave/convexpattern of an information recording medium according to claim 1 andconcave parts formed corresponding to convex parts in the concave/convexpattern of the information recording medium.